Temperature control system



Aug. 4, 1942. M. E. FlENE TEMPERATURE CONTROL SYSTEM 2 Sheets-Sheet 1 Filed Feb. 14, 1941 F131 v I Fig. 2.

a e M n b w m m E S V u n C I w. a o w w m .MTH EC A m .0 0 4 c N m mam FR u 4 0 WT w 7 7 W 7 His Attorney.

Aug. 4, 1942. M. E. FlENE TEMPERATURE CONTROL SYSTEM Filed Feb. 14, 1941 2 Sheets-Sheet 2 inventor": Marcus Fiene,

His Attorney.

Patented Aug. 4, 1942 TEMPERATURE CONTROL SYSTEM Marcus E. Fiene, Caldwell, N. 1., assignor to General Electric Company, a corporation of New York Application February 14 1941, Serial No. 378,913

7 Claims.

My invention relates to control systems and more particularly to temperature control systerm.

It is common in the art of temperature controlling to provide, a modulating or regulating device for controlling the output of conditioning apparatus operating to supply a heating or cooling medium to one or more heat exchangers located in the space or spaces to be conditioned. The regulating device is generally controlled by a single thermostat responsive to the temperature at some place within the conditioned space. It has been found that the temperaturein difierent zones in the conditioned space may vary con siderably with various outside temperature conditions so that, even though the conditioning apparatus functions to maintain a uniform temperature at the location of the thermostat, the temperatures in other zones of the conditioned space fluctuated sufficiently to cause discomfort to the occupant. For example, a variable differential may exist between the temperature of a room in a zone adjacent an outside wall and a temperature in a zone adjacent an inside wall. Also, a variable temperature differential may exist between the breathing line level and the floor line level due to air stratification. Hence it is practically impossible to locate a single thermostat in a conditioned space where it will be responsive to an average temperature condition in the space. This problem is also aggravated by the fact that it is usually necessary to mount the thermostat on a wall where the air temperature may differ considerably from the temperature of the air at other locations within the enclosed space.

Accordingly, it is an object of my invention to provide an improved temperature control system which will maintain constant an average temperature condition of a conditioned space.

More particularly, it is an object of my invention to provide means responsive to the temperatures in different zones of a conditioned space for controlling conditioning apparatus so as to maintain constant an average of the temperature existing in these different zones.

Another object of my invention is to provide an improved regulating device controlled jointly by two condition responsive devices in such a manner that its regulating action is a function of the average of the two regulated conditions.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Briefly, according to my invention, conditioning apparatus such as for example, building heating apparatus, is controlled by a regulating device governing, according to its position, the output of the heating apparatus. The regulating device is controlled by a, reversible operator whose movement is in turn controlled by a pair of twoposition control devices functioning in such a manner that when both of the control devices are aligned in one position the operator moves in one direction and when both of the control devices are aligned in the other position the operator moves in the opposite direction but when the control devices are in different positions the operator remains stationary. Each of the control devices is alternately moved from position to the other by separate timing means, one of which is governed in accordance with one temperature condition and the other being governed in accordance with another temperature condi-' tion. In operation the operator causes the regulating device to assume a mean position such that the average output of the heating apparatus is governed so as to maintain constant an average of the two-temperature conditions which are selected for the purposes of control.

My invention will be better understood from the following description taken in connection with the accompanying drawings in which Fig. 1 illustrates in diagrammatic form one embodiment of my invention, and Figs. 2 and 8 are graphical representations which are useful in explaining the operation of my invention.

For the purpose of illustrating a specific embodiment of my invention I have shown in Fig. l of the drawings temperature changing apparatus comprising a radiator i for supplying heat to a space 2, the temperature of which is to be controlled. The radiator, which may be of the steam or hot water type, is supplied with heating fluid througha main or conduit 3 which is in turn supplied with heating fluid from a suitable source, not shown.

A valve 4 located in conduit 3 acts as a regulating device governing, according to its position,

the heat output of the radiator I. For the purpose of controlling the position of valve 4 I have illustrated an operator in the form'of an electric motor driven mechanism. This mechanism comprises a reversible electric motor, indicated gene'l'ally at 5, which drives a shaft 6 through a suitable reduction gearing'l. Mounted on the end of the shaft 6 is a crank disk 8 carrying a crank pin 9. The crank pin is connected to the operating member of the valve 4 by means of a pitman so that by rotation of the crank disk 8 in one direction or the other the valve'is moved toward either a heat increasing or a heat de-' creasing position. A pair of limit switches H and 2 actuated by a cam |3 mounted on the shaft 6 are provided for preventing overtravel of motor at the closed and open positions: of valve 4.

The reversible motor 5 may be, as illustrated, of the condenser induction type comprising an armature 20 and a pair of field windings2| and 22. The field windings 2| and 22 are connected together at one end thereof and between the opposite ends of the windings is connected a condenser 23. The junction of the field windings 2| and 22 is permanently connected by means of a conductor 24 to the terminal 25a'of the secondary winding 25 of a stepdown transformer 26 having a primary winding 21 energized from a pair of power lines 28 and 29. The other terminals 30 and 3| of the field windings 2| and 22 are selectively connected to the terminal 25b of the secondary winding 25 by the conductors 32 and 33. The arrangement is such that when the conductor 32 is connected to the terminal 25b the capacitor 23 is in series with the winding 22 and when the conductor 33 is connected to the terminal 25b the capacitor 23 is in series with the winding 2|. The current through the winding which is in series with the condenser leads the current through the other winding in phase and thus the direction of rotation of the armature 2| may be controlled by changing the winding in series with the condenser.

For the purpose of controlling the direction of rotation of the motor 5 and consequently the opening and closing movements of the valv 4 I provide a pair of two-position control devices illustrated as relay 35 and36. The relays 35 and 3 36 have sets'of normally closed contacts 38 and 33 and sets of normally open contacts 40 and 4|. The normally closed contacts of both relays are connected in circuit with the conductor 33 and the normally open contacts of bothrelays are connected in circuit with the conductor 32. It

will be evident from an inspection of the circuit connections that when both relays are in the normal or deenergized positions a circuit is completed from the terminal 25b of the transformer secondary winding 25 to the motor terminal 3| causing the motor 5 to rotate in one direction and when both relays are energized a circuit is completed from the terminal 25b of the transformer secondary winding through the conductor 32 to the motor terminal 30 causing rotation of the motor in the opposite direction. It will also be evident that when one relay is energized and the other is deenergized the circuits through both conductors 32 and 33 will be open and the motor is deenergized. One terminal of each of the operating coils 42 and 43 of the relays 35 and 36 is permanently connected to terminal 251) of the transformer secondary winding 25 by means of the conductor 44. The other terminal of the operating coil 43 or relay 36 is connected to the terminal 25a through the conductors 41 and 48 and the contacts of a room thermostat RTI. The other terminal of the operating coil 42 of the relay 35 is connected to the terminal 25a through the conductors 49 and 50 and the contacts of a room thermostat RT2. Thus it will be seen that the energization of the relays 36 and 35 is controlled by the thermostats RT| and RTZrespectively.

The room thermostat RTI is shown as com prising a bimetallic temperature responsive element fixed at one end and carrying at its free end a movable contact 56. The contact 56 cooperates with a stationary contact 51 mounted on a fixed support 58. Also, attached to the support 58 is a permanent magnet 59 which, in cooperatingwith an armature 60 attached to the bimetal 55, acts to give the thermostat a temperature differential of operation in a manner well known in the art.

In order to cause the thermostat contacts to continuously move between the ,open and closed positions and thereby function as temperature responsive timing means, an auxiliary electric heater 6| is provided which is connected to ,be energized when the thermostat contacts are closed and deenergized when the contacts are opened. The energizing circuit for the electric. heater 6| may be traced as follows: terminal 25!: of the transformer secondary winding 25, the conductor 48, the thermostat contacts 56, 51, the bimetal 55, the heater 6|, the conductor 41, the operating'coil 43 of relay 36, conductor 44, and the terminal 25b of the transformer secondary 25. Thus, it will be apparent that when the thermostat contacts 56 and 51 close the heater 6| and the relay 36 will be energized. When the heater 6| has heated the bimetal 55 to the openin point the contacts 56 and 51 open due to a flexing of the bimetal 55 to the-left and heater 6| and relay 36 are deenergized. Due to the heating action of the electric .heater 6| the thermostat contacts continuously open and close causing energization and deenergization of the relay 36 at spaced time intervals which vary in accordance with the temperature at the location of the thermostat RTI. This action will be described in greater detail below.

The construction of the room thermostat RTZ is exactly the same as that of RTI and the cor responding parts have been given like reference numerals. The room thermostat R'I2 causes energization and deenergization of the relay 35 at spaced time intervals which vary in accordance with the temperature at the location of the thermostat RT2.

The room thermostats RT1 and RTz may be located at selected control points in different temperature zones in space 2 and preferably these control points are selected in zones where maximum temperature difierences exist. For example, RT1 may be located adjacent an outside wall and RT2 located adjacent an inside wall in cases where there is a high horizontal temperature gradient due to an outside exposure. In cases where there is a high vertical temperature gradient due to air stratification RT1 may be located at the floor level and RTz' at the breathing line level. The specific location of RT1 and RT: will, of course, vary with different installations, the selected locations depending upon what temperature conditions are desired to be used for the purpose of obtaining an averaged control.

For proper operation of the system each thermostat should be adjusted so that its contacts remain closed 50 per cent of the thermostat cycle time at the desired average temperature to be maintained, which, for the purpose of illustration will be assumed to be 75 degrees F. The adjustment of each thermostat may be and close.

varied by changing the opening and closing temperatures o! the thermostat contacts and by varying the. maximum heating eiIect oi the auxiliary heater GI. However, to secure the proper timing action the maximum heating effect or heater ll must always be greater than the temperature diflerential of operation of the thermostat, i. e., the difference between the temperatures at which the thermostatcontacts open In Fig. 2 of the drawings the curve shows the relationship between the per cent cycle time the thermostat contacts remain closed (R) and the thermostat ambient temperature for the case which will be assumed where the maximum heating eflectoi heater II is 10 degrees F. and the thermostat opening and closing temperatures are 81 and "79 degrees F., respectively. The maximum heating effect of the auxiliary heater II means the number of degrees of temperature it can raisethe thermostat temperature responsive element 'above ambient temperature it it is continuously energized. It will be noted by reference to Fig. 2 that R. equals, 50 per cent when the thermostat ambient temperature is 75 degrees F. It will be understood that the specific temperature values used in this description of my invention are for the purpose of illustration only and other temperature values may be selected as desired.

In operation the thermostats RT! and RT: jointly control the degree of opening of the valve 4 and consequently the output of radiator I. The operation of the system is such that when the average ofthe ambient temperatures at RT1 and RT: is at a. predetermined value the average heat output oi the radiator I remains constant and, an equilibrium condition ob-' tains. Upon any deviation oi this average value from the predetermined value the heat output of the radiator I' is automatically changed in a proper direction until the deviation is reduced to zero and a new equilibrium condition is established at a new radiator heat output.

It is believed that the manner of operation of my improved control system may be best explained by taking a concrete example for thepurpose of illustration. In the subsequent description the following terminology will be used:

To =Outside temperature T1 =Ambient temperature OIVRTI T: =Ambient temperature of RT:

TA=Average of T1 and T:

R1=Per cent of thermostat cycle time of RTI remain closed Rz=Per cent or thermostat cycle time contacts of RT: remain closed Reference will now be made to the chart shown in Fig. 3 of the drawings which illustrates the operation of my improved temperature control system under various conditions operation. The time intervals during which the contacts of RT1 and RT: are in the closed or cold position contacts When both relays II and 36 are energized the closing of contacts 4. and H completes a circuit causing motor to rotate in a direction to open valve 4 and when both relays are deenergized the closing of contacts ll and 38 completes a circuit causing motor 5 to rotate in a direction to close the valve 4. As pointed out above when one relay is energized and the'other is deenergized the motor 5 is deenergized and the valve 4 remains stationary. v g

It follows from the foregoing that when the contacts of both thermostats are closed both relays will be energized and the motor 5 will rotate in a direction to open valve 4. This condition is indicated by the upper shaded areas 0. Likewise, during the time when the contacts of both thermostats are open both relays will be deenergized and the motor I will rotate in a direction to close valve 4. This condition is indicated by the lower shaded areas III. The

curve V shows the variation in the position of valve 4 in per cent of maximum opening with time, the movements of the valve corresponding to the shaded areas 69 and II.

First, let it be assumed that the conditions are such that Tl equals '74 degrees F. and T2 equals '76 degrees F. The operation of the system under these conditions is represented by the portion A of the chart. From the curve shown in Fig. 2 of the drawings it will be noted that R1 equals per cent and R2 equals 40 per cent. Hence the shaded areas are 60 per cent of the cycle time of Rgii and the shaded areas 6 are 40 per cent of the cycle time of RTz. It will be noted that for this condition the shaded areas 68 and Ill are equal which indicates that valve 4 moves alternately equal distances in opposite directions and hence its mean position per cycle and consequently the average heat output of radiator I remains constant. This is the desired condition since Ta is at the predetermined value to be maintained which is '75 degrees F.

Now let it be assumed that To starts to rise so that there is less heat lossirom the space 2. Since the heat supplied by radiator I is greater than required to balance the heat loss from the space 2 the temperatures in space 2 will begin to rise. tion it will be assumed that T1 rises to '76 degrees F. and T: rises to '77 degrees F. so that TA is 76.5 degrees F. which is above the predetermined value of '75 degrees F. to be maintained. This condition is represented by the portion B of the chart. It will be noted that R1 changes to 40 per cent and R2 changes to 30 per cent and as a result the areas 69 become smaller than the areas II. Hence the valve moves in an opening direction a shorter period of time per cycle than in the closing direction and as a result the valve moves in oscillating progression toward a closed position and decreases the average heat output of radiator I.

The net movement of the valve 4 continues in a closing direction until a condition is reached where "TA equals '75 degrees F. Let it be supposed that To rises to a point where there is zero diflerential between T1 and T2. Thus when T1 and T: both equal '75 degrees F. a new equilibrium will be reached since TA also equals '75 degrees F. This condition is indicated by the portion C of the chart. It will be noted that R1 and R2 both equal 50 per cent andthe areas 69 and III are again equal so that the mean position of the valve 4 per cycle is again constant at a new position.

For the purpose of illustra-.

changes in To.

to fall. It will be assumed for illustration that T1 falls to 73 degrees F. and T2 falls to 74 degrees F. so that TA is 73.5 degrees F. This condition is represented by the portion D of the chart. It will be noted that R1 changes ,to 70 parting from my invention in its broader aspects. It will also be understood that my control system is applicable equally well to cooling as well as heating systems.

While I have shown and described particular embodiments of my invention, it will become apparent to those skilled in the art that my 4 invention has other applications and that changes and modifications may be made without departper cent and R2 changes to 60 per cent so that ing from the spirit and scope of my invention.

the areas 69 become larger than the areas 10. Hence the valve 4 moves in oscillating progression toward the open position and the heat output of radiator l is increased.

The opening movement of valve 4 will continue until TA again reaches 75 degrees F. Since it has been assumed that To has fallen to a value lower than its initial value, corresponding to the portion A of the chart, the heat loss I, therefore, aim in the appended claims to cover all such modifications and changes.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a control system for maintaining constant an average of the temperature conditions in two zones, apparatus for changing the temperature conditions in said'zones, a regulating device governing, according to its position, the

of the space II will be greater and hence a new pu of Said pp a reversible motor for equilibrium will not be reached until the valve has opened a greater amount than its initial position. For illustration, it will be assumed that for this new value of To a 4 degree F. differendriving said regulating device, means inculding a pair of two position control devices for controlling said motor, so arranged that when both of said control devices are aligned in one position tial exists between T and T Hence h T 2 said motor drives said regulator in one direction equals 73 degrees F. and T2 equals '77 degrees F. a new equilibriumwill be reached where T5 is again equal to '75 .degrees F. This condition is indicated by the portion E of the chart. It

and when both of said control devices are aligned in the other position said motor drives said regulator in the opposite direction but when said control devices are out of alignment said motor will be noted that R1 changes to 70 per cent n s i u ing vi r n n y,

and R2 changes to 30 per cent and the areas 69 and 10 are again equal so that the mean position of the valve 4 per cycle again remains constant at a new equilibrium position which is further open than the initial position.

It will be apparent from the foregoing that my improved control system -is responsive to variations in both T1 and T2 and functions automatically to maintain their average value TA constant under varying conditions. teresting to note by particular reference to the portions A, C, and E of the chart shown in Fig.3 that even though the temperature differential between T1 and T2 may vary under different conditions or outside temperature the pp a v rsible ele ric m tor for drivaverage output of the radiator remains constant when the average of T1 and T2 reaches a predetermined value. In actual operation the temperatures T1 and T2 will vary gradually with However, for th purpose of cluding the normally closed contacts of both clarity and simplicity of description these changes have been shown as occurring abruptly.

Since my temperature control system is responsive to two temperature conditions of'the aged control that it obtained functions to main- .tain an average temperature condition in the der' the control of a single regulating device functions to change the temperature in both enclosures. In such a case the average of the temperature conditions, in each enclosure would be maintained constant.

It will be understood that, while I have illustrated the operator as controlling the position of a modulating valve, the operator may control the movement of any regulating device which modulates according to its position the output It is in- 40 timing means for moving one of said control devices alternately from one position to the other at spaced time intervals variable in accordance with the tempenature condition in one of said v35 zones and a second timing means for moving the ing said regulating device, a pair of two position circuit controllers, each of said circuit controllers having a set of normally open and a set of normally closed contacts, an energizing circuit inconditioned space, it is obvious that the aver- 5 ment o sa mO in the pp direction.

means for actuating one of said circuit controllers alternately from one position to the other at spaced time intervals variable in accordance with one of said temperature conditions, and

means for actuating the other of said circuit controllers alternately from one position to the -other at spaced time intervals variable in accordance with the other of said temperature conditions.

3. In combination, apparatus for changing the temperature condition in two zones, at regulat-,

ing device for regulating, in accordance with its position, the capacity of said apparatus, a reversible operator for moving said regulator, a pair of control devices having heat increasing and heat decreasing positions for jointly controlling the direction of movement of said operator, means for moving one of said control devices alternately from oneposition to the other at spaced time of temperature changing apparatus without de- 7 intervals variable in accordance with the tempositions.

4. In a system for controlling the output of condition changing apparatus in accordance with an average oitwo variable conditions influenced by the operation of said apparatus, the combination comprising a regulating device for governing according to its position the output of said apparatus, a reversible operator ior driving said regulator, means including a pair oi, two position control devices for controlling the direction of movement of said operator so arranged that when both of said control devices are aligned in one position said motor drives said regulating device in one direction and when both of said control devices are aligned in the other position said operator drives said regulating device in the opposite direction but when said control devices are out of alignment said operator and said regulating device remain stationary, timing means for moving one of said control devices alternately from one position to the other at spaced time intervals variable in accordance with one of said conditions, and a second timing means ior moving the'other of said control devices alternately from one position to the other at spaced time intervals variable in accordance with the other of said conditions.

5. In a control system for maintaining constant an average of the temperature conditions in two "zones, apparatus for changing-the temperature conditions in said zones, a regulating device governing according to its position the output of said apparatus, a thermostat responsive to the temperature in one of said zones, said thermostat having hot" and "cold" positions, an auxiliary heater for locally influencing said thermostat, said heater being energized when said thermostat is in the "col position and deenergized when said thermostat is in the "hot" position whereby said thermostat continuously cycles between hot and "cold positions, a second thermostat responsive to the temperature condition in the other oil said mnes, said second thermostat having hot" and "col positions. an auxiliary heater for locally influencing said second thermostat, said heater for said second thermostat being energized when said second thermostat is in the "cold" position and deenergized when said second thermostat is in the hot tion comprising a regulating device for varying progressively according to its position, the temperature changing eflect or said apparatus, a first controi device, a second control device, each of said control devices having an element movable between first and second control positions, means associated with each control device for causing its movable element to move intermittently be- .tween the first and second control positions,

means responsive to one of said temperature conditions for varying the relative time intervals the movable element'oi said first control device remains in the first and second control positions, means responsive to the other of said temperature conditions for varying the relative time intervals the movable element of said second control device remains in the first and second control positions, and means controlled jointly by said first and second control devices for causing said regulating device to progress in a direction depending on whether the percentage 01 time said control devices are simultaneously in the first control position is greater or less than the percentage of time said control devices are simultaneously in the second control position, the progression 01 said regulating device being zero when said percentages are equal.

7. In a control system for maintaining constant an average of temperature conditions in two zones, apparatus for changing the temperature conditions in said zones, a regulating device governing progressively according to its position the output of said apparatus, a first control device, a second control device, each of said control devices having an element movable between first and second control positions, means associated with each control device for causing its movable element to move intermittently between the first and second control positions, means responsive .ior varying the relative time intervals the movposition whereby said second thermostat continuously cycles between "hot" and "cold podtions, and means controlled by said thermostats for moving said regulating device in the heat increasing direction when both of said thermostats are in the cold" position and for moving said regulating device in the heat decreasing direction when both of said thermostats are in the "hot" position, said means being ineflective to move said regulating device when saidthermostats are in diflerent positions.

8. In a system for controlling temperature changing apparatus in accordance with an average of two temperature conditions, the combinathe temperature condition of one of said zones able element oi said first control device remains in the first and second control positions, the relative time intervals being equal when the temperature condition in the said one of said zones is at a predetermined value, means responsive to the temperature condition in the other of said zones for varying the relative time intervals the movable element'oi said second control device remains in the first and second control positions, the relative time intervals being equal when the temperature condition in the other oi said zones is at said predetermined value, means controlled Jointly by said first and second control devices for actuating said regulating device in one direction when the movable elements 01 said control devices are both in the first control position and in the opposite direction when the movable elements of said control devices are both in 

